New USC process offers faster, cheaper 3D ’printouts’

A University of Southern California inventor has created a machine that can produce 3-dimensional "printouts" in plastic and even metal more quickly and cheaply than widely-used existing systems.

The new machine is a significant improvement on the laser sintering machines now widely used around the world to build complex 3D forms from computer files, according to its creator, Professor Behrokh Khoshnevis of the USC School of Engineering’s Daniel J. Epstein department of Industrial and Systems Engineering.

One patent has been granted and others are pending on the process, which may eventually put 3D object-making within reach of home offices.

The three-dimensional shapes visualized in the computer are re-visualized as stacks of very thin virtual layers. Then, each virtual layer is transformed into a real one.

Sintering machines build up objects by spreading a less- than-1 millimeter thick layer of powdered plastic or other material in a work area, and then melting ("sintering") selected areas, guided by the computer pattern. The process is repeated multiple times, with unmelted powder shaken off or blown away at the end of the process.

The result is to gradually build up complex forms, layer by layer. Such structures as free rolling balls inside of cages, for example, can easily be made.

The objects created were once almost exclusively used as molds or prototypes for die-casting, stamping or other traditional mass-production processes, and this role gave the name "rapid prototyping" to such processes. But with the increasing sophistication of techniques, some companies now use R-P processes - and particularly laser sintering -- for what is now called "direct manufacturing" or "desktop manufacturing" of final products.

Existing machines use a moving laser beam traveling over the work area to do the melting. SIS, for "Selective Inhibition Sintering" instead automatically treats some of the powder applied to resist bonding with adjacent particles under heat, and then exposes the entire piece to uniform, high-intensity heat. Untreated areas of powder sinter. Treated areas do not.

Various anti-sintering materials can be used, including salt water.

Khoshnevis says the SIS process has several advantages over laser machines. The lasers and scanners used in such machines are extremely expensive (up to $100,000 each), short-lived, and energy intensive, he notes, while the heat source for an SIS can be a low- tech gas flame, or an inexpensive electrical heater filament. The cheap, high heat possible with the SIS process makes the use of metals as well as plastics feasible.

Finally, because lasers have to scan out the entire work area, turning on and off to melt the needed areas, they are intrinsically slower in building up pieces, with large, complicated pieces requiring many hours, or even days. The SIS machine can complete a layer in as little as 15 seconds.

The advantages of the process make it possible to see a wider range of use for such machines. "Down the line," says Dr. Khoshnevis, "home offices may have them, right alongside the printer." Shops may have similar, heavier duty units, he said, filling work niches now held by lathes and milling machines.

Khoshnevis now has a working prototype machine, the performance of which he has demonstrated at various conferences.

Khoshnevis’ research was supported by a grant from the National Science Foundation.

Die letzten 5 Focus-News des innovations-reports im Überblick:

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.